The adage tells us that while achieving a goal is difficult, maintaining success is even tougher.

That isn’t always the case in Major League Baseball, but it is accurate for many teams each season. If a club qualifies for the postseason one year, there is zero assurance it will do so the following year.

With Mike Trout, Albert Pujols and Josh Hamilton, the Angels look to be built for October. (AP Photo)

Some teams that earned playoff berths last fall won’t return this October, while others that were absent from last season’s postseason party gladly will fill those vacancies.

How the playoff landscape will change in 2013:

IN: Los Angeles Angels

This team was burdened by high expectations last season and missed the playoffs for the third consecutive year. Adding insult to the Angels’ pain, their AL West rivals, the Oakland A’s and Texas Rangers, earned postseason berths.

The Angels won’t miss the postseason for a fourth consecutive year. With Mike Trout in the lineup for a full season and newcomer Josh Hamilton joining Albert Pujols, the offense shouldn’t struggle out of the gate like it did last spring.

LA’s bullpen is greatly improved and shouldn’t duplicate its 3.97 ERA (12th in the AL last season). And the rotation will have Jered Weaver and a healthy C.J. Wilson, who had bone spurs surgically removed from his pitching elbow after the 2012 season.

It all will translate into a playoff appearance and possibly a deep October run.

OUT: Texas Rangers

While the Angels look like an improved team, the Rangers look like one in decline. Not only did they back into a wild-card berth last season, they were eliminated in their lone postseason game and hardly resembled the powerhouse they had been the previous two Octobers.

The offense not only lost Hamilton to a division rival, it also lost Mike Napoli, who hit 54 homers with a .931 OPS in his two seasons with Texas. Because of the team’s inability to sign or trade for an impact bat during the offseason, that production won’t be easily replaced. In addition, right fielder Nelson Cruz is part of the ongoing Biogenesis investigation and could be suspended for his link to the clinic and performance-enhancing drugs.

The rotation is headed by Yu Darvish, who is in his second major league season after coming over from Japan. It lacks a true ace and failed in its bid to add Zack Greinke, who opted for the money the Los Angeles Dodgers tossed his way.

With the A’s a real threat to repeat as division champs and the Angels set to break their playoff drought, the Rangers will be left out.

IN: Los Angeles Dodgers

They didn’t play well enough in the final month of the 2012 season for all their blockbuster acquisitions to pay off with a playoff appearance. But a full season with that group, which now includes Greinke, should ensure the club will not miss the postseason for a fourth consecutive year.

The offense should be in good shape even with Hanley Ramirez out for about two months, and the rotation trio of Greinke, Clayton Kershaw and Josh Beckett might be one of the NL’s strongest.

Of course, the Dodgers and their record-setting payroll won’t be content to just make the playoffs. Anything less than a World Series title will be considered a failure.

OUT: San Francisco Giants

Considering they came out of nowhere in 2010 and 2012 to win the World Series, lopping the Giants off the list of postseason participants is almost blasphemous. But you only have to look back to 2011 when the team missed the playoffs.

The offense, while no longer completely anemic and featuring the reigning NL MVP (Buster Posey), still has huge question marks. The rotation does as well, mainly Tim Lincecum and, as always, Barry Zito.

Given the Dodgers’ improvement, the Giants will suffer another post-championship letdown.

IN: Kansas City Royals

Spring training statistics usually mean zilch, and the Royals being Cactus League juggernauts this year is no exception. However, this team is no longer immune to regular season success the way it has been since 1985.

General manager Dayton Moore made gutsy trades to improve the rotation, and that will be the main reason Kansas City will transform from a 90-loss squad to a wild-card winner. James Shields and Ervin Santana are huge upgrades, and Wade Davis can be an effective fourth starter.

On the offensive side, youngsters Eric Hosmer, Mike Moustakas, Salvador Perez and Lorenzo Cain should improve enough to help Billy Butler and Alex Gordon make this lineup formidable.

The Royals aren’t ready to upend the Detroit Tigers as AL Central champions, but they are primed to end their 27-year playoff drought.

OUT: Baltimore Orioles

Based on the Pythagorean formula for projecting wins and losses (usually a fairly accurate gauge), the Orioles, thanks to their inept rotation, should have won 82 games last season. But largely because of an incredible bullpen and a lot of homers, they defied the odds and won 93 games and a wild-card spot.

Unless Baltimore’s starting pitchers can improve on their 4.42 ERA from last season, this team will return to reality. With a much-improved Toronto Blue Jays team in the same division, the Orioles won’t pitch well enough to make a second consecutive postseason run.

IN: Toronto Blue Jays

Like the Dodgers in the NL, the Blue Jays made a couple of blockbuster trades to turn themselves legitimate contenders. If Toronto can stay relatively healthy, it will make the playoffs for the first time since 1993 (when it last won it all).

OUT: Oakland A’s or New York Yankees

The Jays’ success has to come at the expense of another of last season’s postseason participants, and the likeliest to fall back are the Yankees and A’s. Toronto was 7-11 against New York last season and 4-5 against Oakland, but those records will improve thanks to the remade rotation and with a healthy and protected Jose Bautista.